Vacuum pump control



Oct. 21, 1941. o. R, FROST VACUUM PUMP CONTROL Filed Feb. 19, 1940 Zmventor Or/eyfayfiaalf Patented ()ci.21,19 41 UNITED STATES PATENT OFFICE 2,260,113 r I I VACUUM PUMP oou'raor.

'0rley Ray Frost, Chicago, 111.

Application February 19, 1940, Serial No. 319,612

2 Claims. (or. 31-13) v 1 of travel ot-the cross-head 34=and withinwhich This invention relates, in general, to vacuum pumps and, in particular, to a new and improved control therefor.

I vacuum established by a vacuum pump whereby the increase in vacuum over the amount desired is prevented.

cylinder casing there is reciprocably mounted a piston 40, said piston being fixedly connected to said cross-head for movement therewith by means such as'a spacing rod 42, and the oppo site sides of said piston being sealed from each other by means such as an. inverted U-shaped Another object is to provide a new and m I proved vacuum control for a vacuum pump which is operable for limiting the vacuum created by the pump to a predetermined value regardless of theability or tendency of the pump to create a greater vacuum.

Another object is to provide in a vacuumpump.

new and improved means whereby the pump is operable'for readily establishing the amount ofvacuum desired and for thereafter maintaining this desired vacuum for the time desired and without increase thereof notwithstanding the continued operation of the suction cycle.

' gasket 44 secured toone face of said piston and extending beyond the other face thereof. Cylinder casing 38, on the sideof piston 40 opposite the side connected to the rod 42, is provided with fa restricted outlet 48 which communicates by Other objects and advantages of the inven-- tion will become readily apparent from a reference to the following specification taken in cona junction with the accompanying sheet of drawings in which- 'Figure 1 is a vertical sectional view through a vacuum pump and showing the invention incorporated therein, and

Fig. 2 is a sectional view of the top portion of the showing in Fig. 1 and being taken at right angles thereto through the axis of the piston therein.

In Figs. 1 and 2 there is shown a standard form. of vacuum pump, generally indicated at I0, which is driven by means such as a motor l2.

Pump it in part comprises, in general, a gear.

casing M which supports a bracket it for the 'means'of the conduit 48, in the case of the .pump chosen for illustration, the pulsating suction and pressure conditions created during, respectively, the downward-and upward strokes of said piston with the desired confined space, such as that space confined within the milkhead (not shown) of a mechanical milking apparatus, or such as any other space into'which it is desired to draw fluid from a source of supply during the a suction stroke of piston 40 and then to discharge said fluid from said-space into another desired space, such as a storage space, during the pressure stroke of said piston.

Previous methods of regulating and controlling the productionof vacuum and attempts 'to motor it, a hearing it in which is Journalled the drive shaft 26 of said motor and on the inner end of which shaft is provided a worm 22, and. a shaft it supported for rotation about its axis by said casing and having fixed thereon a worm wheel 26- in mesh with said worm so as to be driven thereby about said axis, said worm wheel being formed radially outwardly from its axis of rotation-with a crank pin 28 on which pin is pivotally mounted one end of a connecting rod 80, the other end of said rod being pivotally connected, as through a pin 82, to a cross-head M which is reciprocably movable along a fixed path defined by the inner wall 0! a cylindrical guide limit said vacuum to a predetermined amount when once established have been heretofore ineflicient and unreliable and in no way productive oi the desired results. Progress in fields depending upon such vacuum regulation, control and limitation has suffered, therefore, and

. one of said fields, for example, is that which is devoted to mechanical milking wherein it is high-; 1y desirable first, to determine the amount of vacuum necessary together with the-proper timing of its occurrence and duration of its existence and, secondly, to maintain without increase the established vacuum at its predetermined value for'its predetermined duration. Naturally, the

member 36 supported by said casing internally .thereof. Pump It is also provided with a cylintimes of the start and finish of each vacuum stage, as well as the interval between successive stages, can be regulated as desired by proper mechanical attention being givento the length and the reciprocatlve period of the stroke of piston 40, but the amount of vacuum set' up has been more or less uncontrollable as far as the limitation thereof to acertain desired value is concerned, except by relative manipulation of factors such as the displacement of the pump piston, the composite volume of the conduit between the pump and the milkhead and of the vacuum space within the mllkhea'd itself, temof the vacuum to a certain desired value and Y subsequent maintenance thereat. for the desired ginning and ending of said suction stroke, said pump is capable of producing the amount of vacuum desired and that further advance of said piston from said known position would produce a greater vacuum than desired. In order to maintain this desired vacuum without increase thereof after said known piston position has been I reached and until the suction stroke has been completed, a series of openingsill is provided in the wall of cylinder casing 38 progressively from the level of said known piston position to the level of the end of the suction stroke, said openings communicating the suction chamberwithin i said casing with the atmosphere as same are uncovered by the piston during its suction stroke.

Openings 50 are shown individuallyas increasing in area as the suction stroke advances, as

well as being substantially equally spaced from each other, but it is clear that other arrangements with respect to the openings can be substituted, such as, providing openings of equal diameter and increasing the number thereof at each successive level in'the stroke, providing a continuous, downwardly diverging opening, or providing any other atmospheric communicating means which would perform the same or a similar function as-that shown. In operation, the I piston has a continuous suction stroke from beginning to end, and at-or just ahead of the position of the piston whereat, the desired suction is established the suction chamber is communicated with the atmosphere through that inlet, which is shown as being the smallest opening 50, which has an area which permits just.

enoug air therethrough to destroy any additional vacuum which would otherwise be estab-' lished between the then piston position and the position thereof opposite the next inlet means in theprogression. The next air inlet in the progression is so'sized and spaced as to continue the destruction of any otherwise added acuum when the piston has uncovered same, the increase in area of air inlet continuing as 'the piston travels along its suction stroke. It is, therefore, seen preferably formed at its base with a vent or opening 52 which tends to maintain the pressure below piston 4|) (when the latter is near or at the lower end of its stroke) at atmospheric, said opening permitting air egress when said piston has passed on below the lowest opening during its down-stroke and permitting air ingress .before said piston has reached said lowest opening after beginning its up-stroke. Obviously, this maintenance of the pressure at atmospheric when piston 40 is in the vicinity of the lower end of its stroke minimizesthe: load on motor II at that time. It is also to be noted that the wall of casing i4 is provided with an-aperture I4 to open to the atmosphere, whereby'the crosshead 34 will be prevented from producing pressure fluctuations within said casing and the otherwise accompanying motor power wastage eliminated.

Although the invention has been described with some detail it is to be understood that such description is for the purpose of illustration only and is not tobe taken as being definitive of the limits of the. inventive idea. The right is reserved to make such changes in the details of construction and arrangement of parts as will come within the purview of the attached claims.

What I claim is:

1. A pump comprising, a casing having a chamber, a piston movably mounted in said casing for a suction stroke, said piston having a position intermediate the two extreme positions of said stroke whereat said piston is operable for establishing in said chamber a suction of predetermined sub-atmospheric pressure, and means forsubstantially maintaining said predetermined suction during the remainder of said stroke. said means comprising air inlet means formed in the wall of said casing'at substantially the level of said intermediate piston position and extending therebelow forcounteracting the continued pressure reducing effect of the movement of said that the vacuum is first established so that its value is that which is desired, and that this value is thereafter maintained without increase by the provision of properly sized and spaced air inlets which destroy any additive suction.

, ecause of the difference between the cross.

se tional areas of the cylinders formed by casings 38 and 36, the wall ofthe former casing is piston from said intermediate piston position tov the end of'said suction stroke.

2. A pump comprising, a casing having a work ing chamber, a piston mounted in said casing and movable froman initial position whereat' the pressure in said chamber is substantially atmospheric to' a position whreat the pressure in said chamber is substantially below atmospheric, and, means for maintaining said subatmospheric pressure during thecontinued movement of said pistonfrom said second position to the end of the pressure-reducing stroke of said piston, said means comprising air inlet'means formed in the wall of said. casing between the levels of said second position and said stroke end and progressively increasing in inlet area from said level of the former to said level of the latter for counteracting the additive pressure reducing effect of said piston during said continued movement thereof from said second position to said 

